hwc: always_split: Use pipe clock comparison to mixer to split

The layer clock is dependent on vertical downscaling and horizontal
dest width (pixels). When comparing to mixer's requirements,
line-time can be ignored since it is common to both pipe and mixer.
Also since mixer's scale is 1, layer's downscale * dest width needs
to be compared to mixer's width.

Change-Id: I6d28abc33f8a57a15101bf012b7706e163e2dc69
3 files changed